1. Field of the Invention
This invention relates to a sound insulating floor structure of a raised floor, and more particularly to a sound insulating floor structure constructed by a dry-floor construction method so as to form a space between the raised floor and the surface of the existing foundation floor or sub-floor in a variety of buildings such as apartment houses, mansions and the like.
2. Description of the Prior Art
A floor structure comprising an underlying floor layer of a raised floor constructed by supporting a plurality of underlying floor panels at a predetermined height by means of a group of supporting legs installed on a foundation floor or sub-floor via elastic pedestals attached to the lower ends of the supporting legs, intermediate materials laid on the underlying floor layer thus assembled, and floor covering materials laid on the intermediate materials is called a raised dry-floor structure and widely adopted in apartment houses, gymnastics facilities, etc. Such a raised dry-floor structure is devised so that the impact applied to the raised floor may be buffered by the elastic pedestals made of a cushion rubber etc. attached to the lower ends of the supporting legs.
For example, Japanese Patent Application, KOKAI (Early Publication) No. (hereinafter referred to briefly as “JP”) 4-85453 proposes to place on a foundation floor or sub-floor such as concrete slab side by side panel units each comprised of an underlying floor panel and height-adjustable supporting legs attached to the four corners of the panel and provided with elastic pedestals at the lower ends thereof, lay intermediate materials on the panel units, and then lay floor covering materials thereon. JP 3-17348 and Japanese Utility Model Application, KOKAI (Early Publication) No. 4-116537 disclose a method of assembling a raised dry-floor which uses in combination a group of unit supporting legs each comprised of a rod-shaped leg member provided with a rubber pedestal at its lower end rotatably and a support member mounted on the upper end of the rod-shaped leg member in such a manner that it may be moved up and down to adjust the level thereof, and a group of rectangular and/or square underlying floor panels each having a predetermined dimension. This method comprises disposing the unit supporting legs on the surface of a foundation floor at prescribed pitches, and disposing underlying floor panels while leaving predetermined gaps therebetween such that they are supported by the above-mentioned unit supporting legs at positions along their marginal portions.
The floor structure of such configuration is intended to provide a floor surface which will give good feelings of walking or motion owing to the function of the elastic pedestals attached to the lower ends of the supporting legs and which will buffer the impact against the floor surface by the elasticity of the elastic pedestals.
In recent years, however, the propagation of the indoor noises, especially the floor impact noises, to the downstairs poses a serious problem. Since the propagation of the floor impact noises is done not only through the supporting legs but also through the space under the floor and the wall as well, sufficient sound insulation is not acquired only by the elastic pedestals attached to the lower ends of the supporting legs.
Recently, the wood finishing, such as flooring finishing, is widely adopted particularly in the apartment houses instead of using the conventional carpet etc. as a floor covering material. When the wood flooring material is used, however, it will cause aggravation of housing environment because the floor impact noises tend to be directly propagated as a solid-state sound to the foundation floor, as compared with soft floor covering material such as a carpet, and bring loud noises downstairs.
In the case of the flooring to be directly applied, it should have a soft surface in order to improve the sound insulation properties only by the flooring (if it is not soft, the sound insulation properties cannot be improved). However, the soft surface will in turn cause the problems in the floor impact noise insulating properties and in the feel of walking.
Although the sound insulating raised dry-floor has the floor impact noise insulating properties given to the floor frame structure and has been usually finished so as to give a colored floor (flooring), much measures and cost are required to improve the floor impact noise insulating properties. As the measures for coping with the above noise problems, a vibration-damping and sound-insulating sheet, for example, is generally used. As the vibration-damping and sound-insulating sheet, generally a vibration-damping and sound-insulating sheet obtained by forming a sheet from a mixture of an organic binder, such as a synthetic resin or rubber, and a metal powder and adhering a fibrous layer, such as a felt, onto the surface of the sheet is used (see JP 7-90951).
However, it is difficult to fully reduce propagation of the floor impact noises only with such a vibration-damping and sound-insulating sheet. That is to say, the floor impact noises include the light floor impact noise generated by the hard and light impact and represented by the drop sound of tableware, the drag sound of a desk or a chair, the walk sound with slippers, or the like (rapping and tapping sounds) and the heavy floor impact noise generated by the soft and heavy impact such as hopping, jumping down, running about, etc. of people (sounds like a rub-a-dub and a thud). Although the conventional vibration-damping and sound-insulating sheet mentioned above is effective in suppressing the heavy floor impact noise, it is not so effective to the light floor impact noise. To solve such problems, the applicant has also developed a vibration-damping and sound-insulating sheet consisting of an asphalt sheet or a rubber-asphalt sheet containing a metal powder (see JP10-259658). This sheet is effective in improving the sound insulating properties not only for the heavy floor impact noise but also for the light floor impact noise. When such a vibration-damping and sound-insulating sheet is used, however, there is another disadvantage in that the cost for construction of a raised floor will increase. Moreover, a decrease of the durability due to the deterioration of the rubber-based material with long-term use thereof and the other problem should also be considered.